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Most people have spent 700 hours doing one thing or another in their lives, but a number that high is hard to quantify in a relatable way, especially when it comes to exercise. For Scott Kelly, the American astronaut who just returned from spending a year in the International Space Station (ISS), 700 hours represents doctor’s orders—the amount of time NASA required him to spend exercising to inhibit the effects of zero gravity on his body.
Floating in zero gravity might exist as a childhood dream for us earthbound folk, but for astronauts the effects can be all too real. Weakening of muscles, or atrophy, is the most common ailment associated with space travel, but loss of bone density is another key issue—one scientists were keenly focused on given Kelly’s prolonged stay aboard the ISS.
Muscular atrophy and loss in bone density set in for the same reason: the general lack of resistance or necessity to bear weight in zero gravity. When muscles and bones aren’t put to work, they become brittle—a trip to most nursing homes across the country would lend credence to that simple concept.
Special machinery has been developed to help combat this general reduction in muscular mass by simulating gravity, including a bungee cord-equipped treadmill, mechanical bicycle, and weight lifting device.
Bone density loss is just as significant, although somewhat harder to deal with. Astronauts have specially designed and carefully regimented dietary plans that include a number of bone-building supplements, such as calcium and potassium citrate, among others. While the supplements are helpful in theory, the real core of the problem is lack of gravity and weight bearance.
Bone loss sets in immediately upon entering space, but becomes increasingly pronounced several weeks into the trip—a major concern for anyone slated to spend more than a few months, let alone Scott Kelly’s full year, in space. Before more advanced technology existed, astronauts’ bone density would be measured before and after their trips, and researchers would correlate the loss of bone to the given activity aboard the spacecraft and adjust plans accordingly.
A system developed by researchers at Dartmouth College in 2001 changed all that, however, allowing astronauts’ bone loss to be measured in real time by keeping track of urinary calcium, carbon dioxide within the spacecraft, personal medical history, and the aforementioned strict diet and workout routine.
The technology has come even further since then. The European Space Agency, Institute for Biomedical Engineering, and Scanco Medical worked together to create a scanner that produces three-dimensional imaging of bone structures.
This is welcome news not only for astronauts in space, but also for millions of patients who suffer from osteoporosis across the globe. Though the causes of bone loss are fundamentally different, the treatments for reestablishing density are strikingly similar, from the introduction of dietary supplements to regulated exercise.
As medical researchers continually monitor space travelers and patients, more streamlined solutions to bone density loss are bound to be developed and employed throughout the world.
So while the 700 hours Scott Kelly spent exercising in space might seem like a ton—it’s just two days shy of a full month—his regimen represents the next step in how researchers understand bone density and loss both in astronauts beyond our atmosphere and people planted firmly within it.